My external speakers do not work

From TreoCentral

Context

Occasionally, external speakers or Headphones plugged into a Treo do not work.

It is now known that devices that look for a line-input signal (such as any device with an external amplifier) do not provide enough line impedance to cause the Treo to switch modes from mono output with microphone to stereo output on the audio connector.

A: All Treos

Increasing impedance sufficiently on the line will cause the Treo to swtich modes properly. Using a Y adaptor with a set of headphones attached will work. Some have had success adding a stereo volume control in line with the external speakers thereby increasing impedance. It is also possible to wire your own stereo connector and add 500-1000 ohms resistance between the left channel (connector tip) and ground.

Finally, there is an audio coupler available from Seidio that will solve this problem.

Many people use the headphone volume control available at your local Radio Shack.